HARES AND RABBITS
though truncate at the free extremity and hollow; they represent
in a more rudimentary way the much stronger tuft at the end of
the tail of other Porcupines. It is a curious fact that this and
other Porcupines possess a mechanism for warning their foes
precisely comparable to that of the rattlesnake. There are
sixteen dorsal vertebrae.
SUB-ORDER 2. DUPLICIDENTATA.
The chief feature of this group is the existence of two pairs
of incisor teeth in the upper jaw, of which the inner are very
small and lie behind the outer. In the skull the infra-orbital
foramen is small; the incisive foramina are very large. The tail
is short or absent.
Fam. I. Leporidae.—This family is distinguished from the
Lagomyidae by the long ears, by the tail, which is present, though
short, and by the longer limbs. There are six teeth belonging to
the molar series in the upper jaw, and five of the same in the
lower. The clavicle is imperfect.
The longest known genus of this family, Lepus, was, until the
quite recent discovery of Homerolagus, the only genus. It is of
universal range, excepting Australasia and Madagascar, and con-
sists of about sixty species. These are the Hares and Rabbits, to
the former being assigned the longer-limbed forms.
As every text-book of zoology contains a more or less elaborate
account of the structure of the Common Rabbit, and as there is
but little structural difference between the members of the genus,
a short account of the generic peculiarities of Lepus will suffice
here. The fore-feet are five-toed, the hind-limbs four-toed. The
hairy integument enters the mouth cavity, and the inside of the
cheeks have a hairy covering. The soles of the feet are, more-
over, hairy. The maxillary bones are curiously sculptured.
The Common Rabbit, L. cuniculus, differs from the Common
Hare in the comparatively shorter ears and legs. The ears have
not, to so marked a degree, the black tips of those of the Hare.
The animal, moreover, produces naked young, and lives in burrows
of its own excavation. A difference in the structure of the
caecum, which distinguishes the Rabbit from the Hare, has been